Messages in this thread | | | Subject | Re: [PATCH] arm64/mm: fix variable 'tag' set but not used | From | Qian Cai <> | Date | Thu, 1 Aug 2019 08:09:44 -0400 |
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> On Aug 1, 2019, at 8:07 AM, Qian Cai <cai@lca.pw> wrote: > > > >> On Aug 1, 2019, at 8:01 AM, Will Deacon <will@kernel.org> wrote: >> >> On Wed, Jul 31, 2019 at 04:38:18PM -0400, Qian Cai wrote: >>> When CONFIG_KASAN_SW_TAGS=n, set_tag() is compiled away. GCC throws a >>> warning, >>> >>> mm/kasan/common.c: In function '__kasan_kmalloc': >>> mm/kasan/common.c:464:5: warning: variable 'tag' set but not used >>> [-Wunused-but-set-variable] >>> u8 tag = 0xff; >>> ^~~ >>> >>> Fix it by making __tag_set() a static inline function. >>> >>> Signed-off-by: Qian Cai <cai@lca.pw> >>> --- >>> arch/arm64/include/asm/memory.h | 6 +++++- >>> 1 file changed, 5 insertions(+), 1 deletion(-) >>> >>> diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h >>> index b7ba75809751..9645b1340afe 100644 >>> --- a/arch/arm64/include/asm/memory.h >>> +++ b/arch/arm64/include/asm/memory.h >>> @@ -210,7 +210,11 @@ static inline unsigned long kaslr_offset(void) >>> #define __tag_reset(addr) untagged_addr(addr) >>> #define __tag_get(addr) (__u8)((u64)(addr) >> 56) >>> #else >>> -#define __tag_set(addr, tag) (addr) >>> +static inline const void *__tag_set(const void *addr, u8 tag) >>> +{ >>> + return addr; >>> +} >> >> Why doesn't this trigger a warning in page_to_virt(), which passes an >> unsigned long for the address parameter? > > #define page_to_virt(page) … __tag_set(__addr, page_kasan_tag(page)); … > > static inline u8 page_kasan_tag(const struct page *page) > { > return 0xff; > } > > GCC will see that “page” is used.
If you are talking about “addr”,
#define __tag_set(addr, tag) (addr)
It is actually used.
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